Four French soldiers are being questioned Tuesday in an investigation into alleged child rape in Central African Republic, officials said.

It appears to be the first time anyone has faced judicial questioning in the case — at least 19 months after the accusations first surfaced against French troops who were sent to protect Central African civilians displaced by sectarian violence. The disturbing case, long kept secret from the public, has raised questions about how international peacekeeping forces handle suspected abuses by their soldiers.

One of the four soldiers questioned Tuesday has been formally detained, and the others are still being interrogated as suspects, according to Paris prosecutor's office spokeswoman Agnes Thibault-Lecuivre. No one has yet been charged in the case, which is being handled by Paris magistrates.

Fourteen people are reportedly suspected of involvement in the abuses. It's unclear what the four being questioned Tuesday are suspected of. None has been publicly identified.

Several boys described sexual abuse by French troops to U.N. investigators in the Central African Republic capital, Bangui, in May and June 2014. The French defense ministry said it was informed in July 2014 of the accusations, and French prosecutors quickly opened an investigation.

But the accusations weren't made public until April of this year. The French government has not explained why the probe was kept quiet, though France's president promised tough punishment for any soldier found guilty.

Residents of a refugee camp outside Bangui said the soldiers had targeted boys as young as 9 years old, luring them with army rations and small change when their families had nothing to feed them. Some children described to investigators how they were given bottles of water after being raped.

Similar accusations of abuse have emerged against soldiers from Chad and Equatorial Guinea serving in Central African Republic.

France, Central African Republic's former colonial ruler, sent several thousand additional troops to Bangui in late 2013 and in early 2014 amid violence between Christians and Muslims that sent thousands fleeing their homes. The U.N. later sent a 12,000-strong peacekeeping force.